Abstract: :
Purpose: To investigate the survival, integration and differentiationof retinal progenitor cells from GFP transgenic mice after subretinaltransplantation to adult normal pigs.Methods: Retinal progenitorcells derived from postnatal day 1 GFP-transgenic mice weretransplanted subretinally either as single cell suspension,as spheres or as a biodegradable polymer/progenitor compositeto 20 normal non-immunosuppressed adult pigs. Prior to transplantation,small areas of the retina of 10 pigs were damaged with eitherlaser treatment or by mechanical scraping of the neuroretina.The pigs were sacrificed at different intervals ranging from30 minutes to five weeks post-transplantation. The eyes wereimmunohistochemically examined for various progenitor-, retina-,RPE or glial specific antibodies.Results: The GFP expressingmice cells survived well up to 14 days post-transplantation.After 5 weeks, only a few GFP cells were found in 3 out of 6pigs. The cells integrated mainly into the RPE in the non-damagedpig retinas transplanted with cell suspension. In the animalsgrafted with spheres or polymer membranes, no integrating cellswere found, although cells survived in the subretinal spaceeither as spheres or within the membrane. In the pigs receivinglaser treatment prior to grafting of cell suspension, GFP cellswere found integrating into all layers of the retina. Cellsco-expressing PCNA or Ki67 and GFP were only found in the pigsacrificed after 30 minutes. Although the grafted cells ceasedproliferation and in some cases differentiated into cells morphologicallysimilar to mature retinal neurons, only nestin and GFAP co-localizedwith GFP among all the various progenitor-, retina-, RPE orglial specific antibodies used.Conclusions: Our results showthat retinal progenitor cells from GFP transgenic mice can survive,integrate and differentiate in the xenogeneic pig retina. However,the cells do not survive for extended periods, and do not differentiateinto mature RPE or retinal cells. The cells integrate into theRPE and retina only when delivered as a cell suspension. Theretinal integration is markedly enhanced by laser treatmentprior grafting. Allogeneic progenitor cells will likely be bettertolerated, and therefore more useful for studying cell replacementstrategies in large animal models.